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SubjectRe: [PATCH bpf-next 2/3] xdp: xdp_umem: replace kmap on vmap for umem map
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On 13 Aug 2019, at 3:23, Ivan Khoronzhuk wrote:

> For 64-bit there is no reason to use vmap/vunmap, so use page_address
> as it was initially. For 32 bits, in some apps, like in samples
> xdpsock_user.c when number of pgs in use is quite big, the kmap
> memory can be not enough, despite on this, kmap looks like is
> deprecated in such cases as it can block and should be used rather
> for dynamic mm.
>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

Seems a bit overkill - if not high memory, kmap() falls back
to just page_address(), unlike vmap().
--
Jonathan

> ---
> net/xdp/xdp_umem.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index a0607969f8c0..907c9019fe21 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -14,7 +14,7 @@
> #include <linux/netdevice.h>
> #include <linux/rtnetlink.h>
> #include <linux/idr.h>
> -#include <linux/highmem.h>
> +#include <linux/vmalloc.h>
>
> #include "xdp_umem.h"
> #include "xsk_queue.h"
> @@ -167,10 +167,12 @@ void xdp_umem_clear_dev(struct xdp_umem *umem)
>
> static void xdp_umem_unmap_pages(struct xdp_umem *umem)
> {
> +#if BITS_PER_LONG == 32
> unsigned int i;
>
> for (i = 0; i < umem->npgs; i++)
> - kunmap(umem->pgs[i]);
> + vunmap(umem->pages[i].addr);
> +#endif
> }
>
> static void xdp_umem_unpin_pages(struct xdp_umem *umem)
> @@ -378,8 +380,14 @@ static int xdp_umem_reg(struct xdp_umem *umem,
> struct xdp_umem_reg *mr)
> goto out_account;
> }
>
> - for (i = 0; i < umem->npgs; i++)
> - umem->pages[i].addr = kmap(umem->pgs[i]);
> + for (i = 0; i < umem->npgs; i++) {
> +#if BITS_PER_LONG == 32
> + umem->pages[i].addr = vmap(&umem->pgs[i], 1, VM_MAP,
> + PAGE_KERNEL);
> +#else
> + umem->pages[i].addr = page_address(umem->pgs[i]);
> +#endif
> + }
>
> return 0;
>
> --
> 2.17.1

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